Use PhutilNumber in translations

Summary: It's a little bit confusing that you couldn't use %d but kind of expected taken that the number will be formatted so it's not a number anymore.

Test Plan: /paste/

Reviewers: epriestley

Reviewed By: epriestley

CC: aran, Korvin

Differential Revision: https://secure.phabricator.com/D4764

src/applications/differential/controller/DifferentialRevisionViewController.php

@@ -182,10 +182,9 @@ final class DifferentialRevisionViewController extends DifferentialController {
       $warning->setSeverity(AphrontErrorView::SEVERITY_WARNING);
       $warning->appendChild(
         pht(
-          'This diff is very large and affects %2$s files. Load each file '.
+          'This diff is very large and affects %s files. Load each file '.
             'individually.',
-          $count,
-          PhutilTranslator::getInstance()->formatNumber($count)).
+          new PhutilNumber($count)).
         " <strong>".
           phutil_render_tag(
             'a',